Cells are the functional basic unit of life (all living organisms are made of them). They were discovered by Robert Hooke in 1665. The word cell comes from the Latin cellula (a small room). There exist two types of cells: eukaryotic and prokaryotic. Prokaryotic cells are usually independent; we can find them in unicellular organisms, while eukaryotic cells are often found in multicellular organisms. Its basic functions are growth, metabolism (process nutrient molecules), creation (one cell divide into two) and protein synthesis.